JP2003178457A - Optical disk recording method, optical disk recording device and optical disk reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk recording method by which holograms can be continuously recorded and reproduced with at ultra-high density, an optical disk recording device and an optical disk reproducing device. <P>SOLUTION: In recording the holograms in hologram recording regions 7, hologram recording spots HSP to be recorded on one track of the regions 7 and hologram recording spots HSP to be recorded on a track adjacent thereto are recorded in positions different in a circumferential direction. At least one hologram recording spot HSP is recorded in the respective tracks and the process is made continuous. When the diameter of the hologram recording spots HSP is defined as D and the multiple number of the adjacent hologram recording spots HSP as (m), these recording spots are so recorded that the pitch P between the recording spots HSP attains P=D/m. The holograms can therefore be efficiently recorded in the recording regions 7 of the optical disk recording medium 1 at the high density and the higher density of the hologram recording capacity can be attained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording method, an optical disk recording apparatus and an optical disk reproducing apparatus using an optical disk recording medium having a plurality of servo areas at predetermined intervals in the circumferential direction and a hologram recording area between the servo areas. In particular, the present invention relates to an optical disc recording method, an optical disc recording apparatus, and an optical disc reproducing method for continuously recording and reproducing information at ultra-high density by utilizing holography.

[0002]

2. Description of the Related Art Conventionally, a holographic recording method has been known in which information is recorded on an optical disk recording medium by a hologram at an ultrahigh density. In this holographic recording method, an information light carrying image information and a reference light for recording are superposed inside an optical disc recording medium to generate an interference fringe pattern, and the interference fringe pattern is recorded in the optical disc recording medium. The image information is written by. When reproducing information from the recorded interference fringe pattern, the interference fringe pattern recorded in the optical disc recording medium is irradiated with the same reproduction reference light as that used for writing, and diffraction is caused by the interference fringe pattern. To reproduce the image information.

In recent years, attention has been paid to the development of volume holography in which an interference fringe pattern is three-dimensionally written by utilizing the thickness direction of a recording layer of an optical disk recording medium to further increase the recording density. . By utilizing this recording method based on volume holography and further performing multiple recording, the recording capacity of information can be dramatically increased.

An apparatus and method for recording and reproducing information on an optical disk recording medium by such volume holography is disclosed in International Publication No. WO99 / 44195. In order to understand the present invention, the configuration of a recording / reproducing apparatus using volume holography described in the publication will be briefly described. As shown in FIG. 19, the optical disc recording medium 101 includes a circular transparent substrate 10
A hologram recording layer 101c is provided between 1a and 101b, and a reflective film 101d is formed on the surface of the transparent substrate 101b opposite to the recording layer 101c.
A plurality of address servo areas are arranged in the radial direction of the optical disc recording medium 101 at a predetermined angular interval on the reflective film 105, and information recording is performed between these address servo areas arranged in the circumferential direction. The area is provided. In the address servo area, information for performing focus servo control and tracking servo control and address information for the information recording area are recorded in advance by embossed pits. For example, wobble pits can be used as the information for performing the tracking servo control.

As a concrete structure of the optical disk recording medium, the transparent substrates 101a and 101b are, for example, 0.6 mm.
The hologram recording layer 101c has the following appropriate thickness.
However, it has an appropriate thickness of, for example, 10 μm or more. The hologram recording layer 101c is formed of a hologram recording material whose optical characteristics such as a refractive index, a dielectric constant, and a reflectance change according to the intensity of the laser light when irradiated with the laser light for a predetermined time. Photopolymers HRF-600 (product name) manufactured by (Dupont) is used.

As an example of recording on the hologram recording layer by volume holography, as shown in the drawing, an information beam 111 carrying information to be recorded and a recording reference beam 112.
In order to generate interference fringes in the thickness direction in the hologram recording layer 103, the information light 1 is transmitted from the transparent substrate 102 side.
Information is recorded as a three-dimensional hologram by irradiating 11 and the recording reference light 112 for a predetermined time at the same time to stereoscopically fix the interference fringe pattern in the hologram recording layer 103.

[0007]

By the way, in order to realize high-density recording by using a general recording apparatus for optically recording information on a disc-shaped optical disc recording medium, information recording on the optical disc recording medium is required. Higher density can be achieved by narrowing the track pitch of the area, but in the case of hologram recording, the hologram interference area (hologram recording spot) in the hologram recording layer with respect to the track pitch (for example, 0.8 μm). Area (eg φ500μ
Since m) is large, it is necessary to perform the above-described multiplex recording in order to achieve high density. Normally, as shown in FIG. 19, a hologram recording spot on the optical disc recording medium 101 is overlapped with an adjacent spot,
It is possible to record by shifting in the horizontal direction little by little.
In such multiple recording, the diameter of the hologram recording spot is D and the pitch between the hologram recording spots is P.
Then, the multiplex number m is m = D / P.

However, in the above-mentioned multiplex recording, the diffraction efficiency (reproduction light intensity) decreases in proportion to the square of the multiplex number m of the hologram, so that the improvement of the recording density and the assurance of the reproduction light intensity are taken into consideration. It is necessary to obtain the optimum multiplex number in advance and determine the pitch of the hologram recording spot on the recording layer based on the optimum multiplex number. Even in this case, the determined hologram recording spot pitch (P) itself is larger than the track pitch of the information recording area of the optical disc recording medium (for example, 20 μm). For this reason, if holograms are continuously written in the hologram recording layer 103 at the pitch P of the hologram recording spot determined as it is, burst recording is performed such that recording can be performed on one track but cannot be performed on another track. Become.
It is difficult to continuously reproduce the hologram thus recorded in a burst manner.

The present invention has been made in view of the above circumstances, and provides an optical disk recording method, an optical disk recording apparatus, and an optical disk reproducing apparatus capable of continuously recording / reproducing a hologram at an ultrahigh density. With the goal.

[0010]

In the recording method for an optical disk recording medium according to the present invention, servo areas for tracking servo, focus servo and clock generation of an optical head are discretely formed at predetermined intervals in the circumferential direction. A hologram recording area, which is a mirror area when not recorded, is formed between the servo areas, and an interference pattern due to interference between the information light emitted from the optical head and the recording reference light is formed in the hologram recording area. In a recording method of an optical disc recording medium in which is recorded as a hologram, a hologram recording spot recorded on one track of the hologram recording area and a hologram recording spot recorded on a track adjacent to the hologram recording area are circumferentially arranged. At different positions, and the pitch P between adjacent hologram recording spots is The diameter of the program D, the multiple number of preset holographic recording spot and m, P
It is characterized in that the hologram is recorded in the hologram recording area such that = D / m.

According to the recording method of the optical disk recording medium of the present invention, when recording a hologram in the hologram recording area, the hologram recording spot recorded on one track of the hologram recording area and the track adjacent to the hologram recording spot are recorded. Since the hologram recording spots to be recorded are recorded at different positions in the circumferential direction, at least one hologram recording spot is formed on each track, and if the hologram recording and reproducing operations are performed in a burst manner. Instead, it becomes a continuous process. Moreover, according to the recording method of the present invention, the diameter of the hologram recording spot is set to D
When the number of multiplexed hologram recording spots is m, the pitch P between adjacent hologram recording spots is P =
Record so that it becomes D / m. Therefore, it is possible to efficiently record the hologram in the hologram recording area of the optical disc recording medium with high density, and it is possible to increase the density of the hologram recording capacity.

In the above recording method, the distance between the hologram recording spot recorded on one track of the hologram recording area and the hologram recording spot recorded on the adjacent track is approximately P, Hologram recording spot recorded on one track,
It is conceivable to record a hologram in the hologram recording area so that the positions of the hologram recording spots recorded on tracks distant by m tracks become equal. By recording in this way, it is possible to realize high-density recording and simplify processing.

In the above recording method, the distance between the hologram recording spot recorded on one track of the hologram recording area and the hologram recording spot recorded on the adjacent track is approximately P, and 1 Hologram recording spots recorded on one track and m
A hologram may be recorded in the hologram recording area such that the circumferential position of the hologram recording spot recorded on a track separated from the track is displaced by P / 2. By recording in this way, higher density recording can be realized.

In such a recording method, the optical disk recording medium is divided into a plurality of zones in the radial direction, and the number of holograms recorded in the circumferential direction of one hologram recording area in the outer peripheral side zone is the inner peripheral side. It is preferable to record holograms in the hologram recording area so that the number of holograms is greater than the number of holograms recorded in the circumferential direction of one hologram recording area in the side zone. Thereby, the recording density can be increased.

In the optical disk recording apparatus according to the present invention, servo areas for tracking servo, focus servo and clock generation of the optical head are discretely formed at predetermined intervals in the circumferential direction, and between the servo areas, An optical disk recording medium in which a hologram recording area, which is a mirror area when not recorded, is formed, and an interference pattern due to interference between the information light emitted from the optical head and the recording reference light is recorded as a hologram in the hologram recording area. On the other hand, in the optical disk recording apparatus for recording the hologram, a clock generating means for generating a clock by reading the information in the servo area of the optical disk recording medium with the optical head, and a clock generated by the clock generating means as a reference Recording timing signal that determines the recording timing for each track And a hologram recording spot recorded on one track of the hologram recording area and a hologram recording spot recorded on a track adjacent to the hologram recording spot. , The pitch P between adjacent hologram recording spots recorded at different positions in the circumferential direction is P = D /, where D is the diameter of the hologram recording spot and m is the preset multiplex number of hologram recording spots. The recording timing of the hologram in the hologram recording area is determined so that m becomes m.

In the optical disk reproducing apparatus according to the present invention, servo areas for tracking servo, focus servo and clock generation of the optical head are discretely formed at predetermined intervals in the circumferential direction, and between the servo areas, In an optical disk reproducing device for reproducing an optical disk recording medium having a hologram recording area in which an interference pattern due to interference between information light emitted from the optical head and recording reference light is recorded as a hologram, a servo of the optical disk recording medium is provided. A clock generating means for generating a clock by reading the area information with the optical head, and a reproduction timing generating means for generating a reproduction timing signal for determining a reproduction timing for each track based on the clock generated by the clock generating means. And the reproduction timing generation means is The hologram recording spot recorded on one track of the gram recording area and the hologram recording spot recorded on the adjacent track are recorded at different positions in the circumferential direction, and between the adjacent hologram recording spots. When the pitch P is the diameter of the hologram recording spot and the preset multiplex number of the hologram recording spot is m, the reproduction timing of the hologram recording spot from the hologram recording area is P = D / m. It is characterized by determining.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram for explaining an optical disc recording medium used in an optical disc recording apparatus according to an embodiment of the present invention, FIG. 2A and FIG.
B is a partially enlarged view of FIG. 1. As shown in FIG. 1, a disc-shaped optical disc recording medium 1 includes a plurality of frames 2 (in this example, frames # 00 to # 9) divided in the circumferential direction.
7) and each of these frames 2 is further divided into a plurality of segments 3 (in this example, segment #
00 to # 13). Each segment 3
Includes a servo area 6 and a hologram recording area 7 except for some of the adjacent servo areas 6, and between some of the adjacent servo areas 6 (in this example, the servo area 6 of the segment # 00 and An address area 8 in which address information indicating an access position is recorded is formed between the servo areas 6 of the segment # 01.

As shown in FIGS. 2A and 2B, in each servo area 6, a servo clock pit SCK serving as a reference for the timing of various operations in the optical disk recording / reproducing apparatus.
1, 2, and 3 and servo pits A, B, and C for performing focus servo and tracking servo by, for example, a sampled servo system are recorded in advance by embossed pits or the like. The address area 8 includes a preamble 8a, a sync mark 8b, an address part 8c, an end address mark 8d, a post sync mark 8e and a post mark.
It is composed of an amble 8f.

In the address part 8c, address information for identifying the hologram recording area 7 is recorded every other track. When recording a hologram, the information recorded in this address area 8 is used. Then, the irradiation positions of the information light, the recording reference light, and the reproduction reference light from the optical head are aligned with the information recording position of each hologram recording area 7. The optical disc recording / reproducing apparatus is configured to record the servo clock pit SCK recorded in the servo area 6.
1 to 3 and the servo pits A, B, and C are used for focusing and tracking, and the address light recorded in the address area 8 is detected to detect the information light in each hologram recording area 7, the recording reference light, and the recording light. The irradiation position of the reproduction reference light is adjusted. Hologram recording area 7
Is a mirror area that is not physically formatted with embossed bits.

FIG. 3 is an enlarged partial sectional view of the optical disk recording medium 1. In the optical disk recording medium 1, a hologram recording layer 1c is provided between circular transparent substrates 1a and 1b, and a reflective film 1d is formed on the surface of the transparent substrate 1b opposite to the recording layer 1c. It is composed by pasting. On the reflective film 1d, the embossed pits of the servo area 6 and the address area 8 are pre-formatted as the physical format in the segment # 00, and only the embossed pits of the servo area 6 are pre-formatted as the physical format in the segments # 01 to # 13. Has been done. In this way, by using only one of the 14 segments for the physical format of the address information, the area of the mirror area that can be used for recording the hologram can be secured as large as possible. In the hologram recording area 7, the hologram recording spot HSP having the diameter D is recorded while being shifted by the pitch P in the horizontal direction so as to partially overlap with the adjacent spot HSP, thereby realizing multiple recording.

As a concrete structure of the optical disk recording medium, the thickness t1 and t3 of the transparent substrates 1a and 1b are, for example, 0.6 mm or less, and the thickness t2 of the hologram recording layer 1c.
Is set to, for example, 10 μm or more. When the hologram recording layer 1c is irradiated with laser light for a predetermined time,
It is formed of a hologram recording material whose optical properties such as a refractive index, a dielectric constant, and a reflectance change according to the intensity of laser light. For example, Photopolymers HRF-600 (product name manufactured by Dupont) is used. ) Etc. are used.

Next, the physical format of the servo area 6 and the address area 8 will be described in detail. As shown in FIGS. 2A and 2B, the servo clock pits are formed at both ends of the servo pits A, B, and C forming areas.
Servo clock pit SCK1 formed at one end
Is formed in the track direction, and two servo clock pits SCK2 and SCK3 formed at the other end are continuously formed in the track direction. This allows servo clock pits SCK1 and SCK2, SC to determine directionality in order to enable bidirectional reading in the track direction.
The number of K3 formed is different. By forming the servo clock pits SCK1, SCK2, SCK3 in this way, the servo clock information differs depending on the difference in the reading direction, so that the reading direction can be identified. This is a function necessary for executing the tracking servo processing described later.

In the optical disc recording medium 1 of this embodiment, tracks are formed between these embossed pits.
The array pitch in the radial direction of the servo clock pits SCK1 to SCK3 is equal to the track pitch (for example, 0.8 μm),
This is the spatial frequency (λ / 2N) of MTF = 0 shown in FIG.
A) is set. As a result, the servo clock pits optically appear as one groove in the radial direction, and it is possible to detect any position of the light beam at the start of tracking. The same applies to the preamble 8a, the synchronization mark 8b, the end address mark 8d, the post synchronization mark 8e, and the postamble 8f in the address area 8.

Servo pits A, B and C are sampled.
It realizes a servo. That is, as shown in FIG. 5, the servo pit A'formed at the on-track position is formed.
And the servo pits B'and C'arranged to the left and right in the direction of travel of the track, pits A ', B', and C'are formed with a 1/2 track pitch (TP). Inevitably, the manufacturing cost rises, but in the method of the present embodiment, all pits are formed between tracks as shown in FIG. Since the on-track position is detected by a pair of pits, the pit formation accuracy is the track pitch (TP), and the manufacturing cost can be reduced accordingly.

In FIG. 3A, the light beam spot S
When P is on-track to the A track (A-Tr), the light beam spot SP first detects two pits A, and then detects one pit B and one pit respectively. As shown in the figure (b), the first detection signal RFA is maximum, and the second and third detection signals RF that follow are the maximum.
The amplitudes of B and RFC are smaller than that of RFA, and have substantially the same amplitude. Therefore, in this case, the tracking error signal TE can be obtained by subtracting the peak values of the detection signals RFB and RFC having a small amplitude as sample and hold.

Next, the address part 8c will be described. In the address part 8c, address information is recorded every other track. FIG. 7 shows an arrangement relationship between each track and each frame and address information.
As shown in this figure, the address information is recorded in an odd frame in the case of an odd track (exactly outside the odd track) and in an even frame in the case of an even track (exactly outside the even track). It The address information consists of, for example, 2-byte track number information and 1-byte frame number information. While the odd-numbered track is being accessed, the track information and the frame information are referenced from the address area 8 of the odd-numbered frame, but only the frame information is referenced from the address information 8 of the even-numbered frame, and the track information is not referenced. Similarly, while accessing the even-numbered track, the track information and the frame information are referenced from the address area 8 of the even-numbered frame, but only the frame information is referenced from the address information 8 of the odd-numbered frame, and the track information is not referenced. By performing such address reference, it is possible to reduce the spatial frequency in the radial direction even if the track density reaches the spatial frequency of MTF = 0.
It is possible to refer to the address without any trouble.

Next, the hologram recording format (logical format) in the hologram recording area 7 will be described. FIG. 8 is a diagram for explaining the hologram recording format. The circles shown in the figure are for convenience of explanation.
It should be noted that it shows the central portion of the recording position of the hologram recording spot, and does not represent the hologram recording spot. As shown in FIG. 3, the radius D of the hologram recording spot HSP is much larger than the track pitch TP (0.8 μm in this example). Now, assuming that the radius D of the hologram recording spot HSP is 500 μm and the multiplexing number m is 25, the recording pitch P of the hologram recording spot HSP is D / m = 20 μm. Therefore, when hologram recording spots HSP are continuously formed on one track at a pitch of 20 μm, the next recordable track is a track 25 tracks ahead.
In this case, continuous recording / reproduction becomes impossible.

Therefore, in this embodiment, after the hologram recording spot HSP is formed on one track, the hologram recording spot HSP is recorded on the next track at a position displaced by the pitch P (= 20 μm) in the track direction. By repeating this in sequence, the hologram recording spot HSP is formed on the track m (= 25) tracks ahead at the same radial position as the first track. As a result, since at least one hologram recording spot is recorded or reproduced on each track without fail, continuous processing is possible.

FIG. 9 shows a recording pulse that gives timing at the time of recording. Based on the servo clock CK reproduced from the servo clock pit SCK1 of the servo area 6, the write timings are respectively shifted on the tracks # 00, # 01, ..., #n. This shift amount corresponds to the pitch P.

FIG. 10 is a diagram showing another embodiment of the hologram recording format. In this embodiment, the hologram recording spot rows that are adjacent to each other in the radial direction are displaced by about P / 2. By arranging in this way, it is possible to arrange the hologram recording spots at a higher density.

As shown in FIG. 11, the optical disk recording medium 1 has a plurality of zones ZA, Z in the radial direction, for example.
B, ZC are formed, and the number of hologram recording spots HSP recorded in each zone ZA, ZB, ZC is set to n1, n2, n3 (where n1 <n2
You may make it change like <n3). With such an arrangement, the recording density is further improved.

FIG. 12 is a block diagram schematically showing the structure of an optical disk recording / reproducing apparatus according to an embodiment of the present invention. The optical disc recording / reproducing apparatus 10 includes a spindle 41 to which the optical disc recording medium 1 is attached, a spindle motor 42 for rotating the spindle 41,
The optical disk recording medium 1 is provided with a spindle servo circuit 43 for controlling the spindle motor 42 so as to keep the rotational speed at a predetermined value. Further, the optical disc recording / reproducing apparatus 10 irradiates the optical disc recording medium 1 with the information light and the recording reference light to record a hologram in the hologram recording area 7, and at the same time, records the hologram on the optical disc recording medium 1. The optical head 40 for reproducing the original information from the hologram recorded in the hologram recording area 7 of the optical disc recording medium 1 by irradiating the reproducing reference light to detect the reproduced light, and the optical head 40. The optical disk recording medium 1 is provided with a drive device 44 that is driven in the radial direction.

The optical disc recording / reproducing apparatus 10 detects the focus error signal FE, the tracking error signal TE, the tracking error signal CE from the output signal of the optical head 40,
A detection circuit 45 for detecting the reproduction signal RF and a focus error signal F detected by the detection circuit 45.
While the optical head 40 passes through the servo area 6 based on E and a command from the controller 50, a focus servo for moving the optical head main body described later in a direction perpendicular to the plate surface of the optical disc recording medium 1 to perform focus servo control. And a circuit 46. Further, while the optical head 40 passes through the servo area 6 based on the tracking error signal TE detected by the detection circuit 45 and the command from the controller 50, the optical head main body is moved in the radial direction of the optical disc recording medium 1 to perform tracking. A tracking servo circuit 47 for performing servo control, a tracking error signal CE detected by the detection circuit 45, and a controller 50.
While the optical head 40 passes through the hologram recording area 7 on the basis of the command from, the optical head main body is moved in the moving direction of the optical disc recording medium 1 to move the information recording position of the hologram recording area 7 to the information light and the recording reference light. And a tracking servo circuit 55 that performs tracking servo control so that the irradiation position of the track No. 2 follows the position without shifting for a predetermined time. Furthermore, the controller 50 controls the drive device 44 based on the tracking error signal TE and the command from the controller 50 to perform the slide servo control for moving the optical head 40 in the radial direction of the optical disc recording medium 1, and the controller 50. And a follow-up control circuit 54 for making the optical head 40 follow a desired information recording position while the optical head 40 passes through the servo area 6 based on the above command.

Further, the optical disk recording / reproducing apparatus 10 is
The hologram recorded at each information recording position of the hologram recording area 7 of the optical disc recording medium 1 is reproduced by decoding the output data of a CCD array described later in the optical head 40, or the reproduction signal RF from the detection circuit 45 is used as a basic signal. A signal processing circuit 49 for reproducing a clock to supply a clock signal to the controller 50 and for determining address information in the address area 8, and an optical disk recording / reproducing apparatus 10.
The controller 50 is provided with a controller 50 for controlling the overall operation of the controller 50 and an operation section 51 for giving various instructions to the controller 50.

Further, the optical disk recording / reproducing apparatus 10 is
A tilt detection circuit 52 that detects a relative tilt between the optical disk recording medium 1 and the optical head main body based on an output signal of the signal processing circuit 49, and a plate of the optical disk recording medium 1 based on an output signal of the tilt detection circuit 52. An inclination correction circuit 53 is provided which changes the position of the optical head main body in a direction in which the inclination of the optical head main body with respect to the surface changes to correct the relative inclination between the optical disk recording medium 1 and the optical head main body.

The portion of the signal processing circuit 49 related to the tracking error detection circuit is constructed as shown in FIG. 13, for example. Values RFA, RF obtained by sampling / holding the peak values of the RF signal from the detection circuit 45 at the points A, B, C with the servo clock CK as a reference.
The difference between B and RFC is calculated by the differential amplifier 61a,
It is determined by 61b and 61c. These differential amplifiers 61a, 6
The outputs TPA, TPB, and TPC of 1b and 61c are selected by the multiplexer 62 and the tracking error signal TE is selected.
Is output. The polarities of the outputs of the differential amplifiers 61a, 61b, 61c are compared with the comparators 63a, 63b, 63, respectively.
c to detect these comparators 63a, 63b, 63
The logical operation circuit 64 controls switching of the multiplexer 62 based on the outputs PA, PB, and PC of c. As a result, the difference between the two small peak values shown in FIG. 6B is output as the tracking error signal TE. Incidentally, these tracking error signals TRA, TRB,
The dynamic range of TRC is, as shown in FIG. 2A,
This is due to diffraction in the two servo pits 65, and can be made a large value compared with the conventional optical disc, in other words, a tracking error signal TE having a good S / N ratio (signal to noise ratio) can be obtained. it can.

In the optical disc recording / reproducing apparatus 10, during recording of a hologram, the optical head 40 is moved in a direction substantially along the track while the optical head 40 passes through the servo area 6, thereby moving the hologram for a predetermined time. A tracking control circuit 54 for controlling the irradiation position of the information light and the recording reference light is provided so that the irradiation position of the information light and the recording reference light follows one information recording position of the recording area 7. In the embodiment, in order to perform tracking servo control so that the irradiation positions of the information light and the reference light for recording track the information recording position more precisely and accurately, the detection circuit 45 detects the information recording position of each information recording position of the hologram recording area 7. The positional deviation in the moving direction of the optical disk recording medium 1 from the irradiation position of the information light and the recording reference light is determined by the servo clock pit S
CK1 to CK3 are irradiated with a laser beam for a tracking servo and detected as a tracking error signal CE.
A tracking servo circuit 55 is provided for performing tracking servo by moving the optical head main body in the moving direction of the optical disk recording medium 1 even within the hologram recording area 7 based on E.

The controller 50 inputs the servo clock CK and the address information output from the signal processing circuit 49, and also the optical head 40 and the spindle servo circuit 4
3, slide servo circuit 48, focus servo circuit 4
6, tracking servo circuit 47, tracking servo circuit 55
The tracking control circuit 54 and the like are controlled.
The basic clock output from the signal processing circuit 49 is input to the spindle servo circuit 43. Controller 5
0 has a CPU (central processing unit), a ROM (read only memory) and a RAM (random access memory).
By executing the program stored in M, the function of the controller 50 is realized.

Next, referring to FIG. 14, the optical system 1 of the optical head 40 of the optical disk recording / reproducing apparatus according to the present embodiment.
An example of No. 1 will be described. For hologram recording on the optical disk recording medium 1, a divergent laser beam emitted from a laser source 25 is focused by a lens 24 to form a laser beam, and this laser beam is split into two laser beams using a half mirror 30a. Then, one is used as the information light modulated by the recording information and the other is used as the recording reference light for forming the interference pattern. That is, in recording a hologram, the information light and the recording reference light are recorded on the optical disc recording medium 1 so that a three-dimensional interference fringe pattern is formed in the hologram recording layer 1c due to the interference between the information light and the recording reference light. This is performed by irradiating the hologram recording layer 1c for a predetermined time. In order to irradiate one of the information recording positions of the hologram recording layer 1c of the optical disk recording medium 1 with the information light and the recording reference light for a predetermined time, the optical disk recording medium 1 is moved and the irradiation position of the optical head 40 is moved. And are synchronized for a predetermined time.

That is, it is necessary to move in synchronization with the time required for exposure accurately. Therefore, in the present embodiment, the servo clock pits SCK1 to SCK1 to SCK3 are formed in the servo area 6.
And irradiating the servo clock pits SCK1 to SCK1 to 3 with a tracking laser beam having a wavelength different from the wavelength of the laser beam for hologram recording, thereby setting the information recording position and the irradiation position of the information light and the recording reference light. The position of the position is detected, and tracking servo control for accurately aligning the information recording position of the hologram recording area 7 and the irradiation position of the information light and the recording reference light for a predetermined time at the time of recording the hologram is performed. Is going. Further, the reproduction of the recorded hologram is performed by irradiating the hologram recording layer 1c with the reproduction reference light instead of the recording reference light for forming the interference pattern.

Further, an example of the optical system shown in FIG. 14 is a schematic view showing the principle of the optical part of the optical head used in the optical disk recording / reproducing apparatus of this embodiment. The optical head 11 includes an objective lens 12 facing the optical disc recording medium 1 and the objective lens 1
An actuator 13 for moving the optical disc recording medium 1 in the thickness direction and the radial direction of the optical disc recording medium 1, and on the light source side of the objective lens 12, a two-part optical rotation plate 14 in order from the objective lens 12.
And the prism block 15 are arranged, and the two-divided optical rotation plate 1
Reference numeral 4 includes an optical rotation plate 14L arranged on the left side of the optical axis and an optical rotation plate 14R arranged on the right side of the optical axis. The optical rotation plate 14L rotates the polarization direction of the laser beam by + 45 °, and the optical rotation plate 14R rotates the polarization direction of the laser beam by -45 °. Prism block 15
Has a half mirror 15a and a total reflection mirror 15b in this order from the two-divided optical rotation plate 14 side. Both the half mirror 15a and the total reflection mirror 15b are arranged such that their normal directions are inclined by 45 ° in the same direction with respect to the optical axis of the objective lens 12.

On the side of the prism block 15, further,
Another prism block 19 is arranged in parallel, and the total reflection mirror 19a of the prism block 19 is arranged in parallel so as to face the half mirror 15a of the prism block 15. Similarly, the total reflection mirror 15 of the prism block 15
Half mirror 1 of prism block 19 facing b
9b are arranged in parallel. A prism block 23 having a half mirror 23a and a prism block 30 having a half mirror 30a are further arranged beside the prism block 19.

Half mirror 15 of prism block 15
The convex lens 16 and the phase spatial light modulator 17 are disposed between a and the total reflection mirror 19a of the prism block 19, and between the total reflection mirror 15b of the prism block 15 and the half mirror 19b of the prism block 19. A spatial light modulator 18 is arranged. Phase spatial light modulator 1
Reference numeral 7 has a large number of minute sections arranged in a grid pattern, and the phase of the laser beam passing through each minute section can be changed and the phase of the passing laser beam can be spatially modulated. The reference light is generated during hologram formation or hologram reading, and can be easily realized by using a liquid crystal element.

On the other hand, the spatial light modulator 18 functions as an information light generating means, and its structure is composed of a large number of minute sections arranged in a lattice like the optical modulator 17, and a laser beam is provided for each minute section. It is possible to spatially modulate the intensity of the laser beam and generate information light carrying information by selecting the passing state and the blocking state according to the information to be recorded. Like the phase spatial light modulator 17, a liquid crystal element can be adopted for the spatial light modulator 18.

The light source of the optical head 11 converges the coherent divergent laser light from the laser light source 25 for hologram recording / reproducing, the laser light source 33 for tracking servo, and the laser light sources 25, 33 into a parallel light beam to form a laser beam. The half mirrors 23a and 30a provided with the collimator lenses 24 and 32, respectively, and provided on the prism blocks 23 and 30, respectively, are inclined by 45 ° with respect to the optical axis of the collimator lenses 24 and 32 in the normal direction. . Laser light source 2 that passes through these half mirrors 23a and 30a
A part of the projected light from 5, 33 is generated by the photo detector 2.
The outputs of the photodetectors 26 and 31 are automatically adjusted to the light outputs from the light sources 25 and 33.

The return beam from the optical disk recording medium 1 is reflected by the half mirror 23a, passes through the convex lens 27 and the cylindrical lens 28 provided on the side opposite to the photodetector 26, reaches the four-division photodetector 29, and reaches the optical head 40. While passing through the address servo area 6, the focus error signal FE and the tracking error signal TE are detected and the reproduction signal RF is derived. The detected focus error signal FE is used for focus servo control of the optical head 40, and the tracking error signal TE is used as the tracking error signal TE.
Used to perform zero tracking servo control.

In the present embodiment, when the optical head 40 passes through the hologram recording area 7, the tracking error signal CE is detected to perform the tracking servo control of the optical head 40.
The irradiation position of the laser beam for tracking servo on the servo clock pit can be moved by displacing the emission position of the laser light source for tracking servo from the optical axis of the collimator lens 32 according to the hologram recording mode. . Therefore, the laser beam for tracking servo irradiates the servo clock pits SCK1 to SCK3 to detect the tracking error signal CE, and while performing the tracking servo control, the information recording position is irradiated with the laser beam for hologram recording, It is configured so that a hologram can be recorded.

Next, the outline of the operation for recording a hologram will be described. In FIG. 14, during hologram recording, the spatial light modulator 18 has a transmissive state (hereinafter also referred to as “on”) and a blocked state (hereinafter also referred to as “off”) for each pixel according to the information to be recorded. Is selected to spatially modulate the passing laser beam to generate information light. In the embodiment of the present invention, two pixels represent 1-bit information,
Be sure to turn on one of the two pixels corresponding to 1-bit information and turn off the other.

Further, the phase spatial light modulator 17 follows the predetermined modulation pattern with respect to the passing laser beam.
Phase difference 0 (rad) for each pixel based on a predetermined phase
By selectively applying or π (rad), the phase of the laser beam is spatially modulated, and the recording reference light in which the phase of the laser beam is spatially modulated is generated. The controller 50 provides the phase spatial light modulator 17 with information of the modulation pattern selected by itself or the modulation pattern selected by the operation unit 51 according to a predetermined condition, and the phase spatial light modulator 17 is provided by the controller 50. , Or the phase of the passing laser beam is spatially modulated according to the information of the modulation pattern selected by the operation unit 51.

The laser beam output from the laser light source 25 has a pulsed high output for recording. The controller 50 predicts the timing at which the laser beam emitted from the objective lens 12 passes through the hologram recording area 7 based on the basic clock reproduced from the reproduction signal RF, and the light emitted from the objective lens 12 is emitted from the hologram recording area 7. The above setting is maintained while passing through. Further, while the laser beam from the objective lens 12 passes through the hologram recording area 7, focus servo control and tracking servo control are not performed and only tracking servo control is performed. Further, in the following description, it is assumed that the laser light source 25 emits P-polarized light.

As shown in FIG. 14, the P-polarized laser light emitted from the laser light source 25 is emitted from the collimator lens 2
It is converted into a parallel light beam by 4 and passes through the beam splitter 30 to enter the beam splitter 23.
Part of the amount of light passes through the half mirror 23a and enters the prism block 19. A part of the light amount of the laser beam incident on the prism block 19 passes through the half mirror 19b and then passes through the spatial light modulator 18. At that time, the laser beam is spatially modulated according to the information to be recorded, and becomes the information light. Become.

This information light is reflected by the total reflection surface 15b of the prism block 15, and a part of the light amount is reflected by the half mirror 1.
After passing through 5a, it passes through the two-part optical rotation plate 14. Here, the laser beam that has passed through the optical rotation plate 14L of the two-part optical rotation plate 14 has its polarization direction rotated by + 45 ° to become an A-polarized laser beam, and the light that has passed through the optical rotation plate 14R has its polarization direction rotated by −45 °. It becomes a B-polarized laser beam. The information light of A-polarized light and B-polarized light that has passed through the two-division optical rotation plate 14 is
Hologram recording layer 1c and substrate 4 of optical disc recording medium 1
The optical disc recording medium 1 is irradiated by the objective lens 12 so as to converge on the boundary surface of the reflective film 1d.

On the other hand, the laser beam reflected by the half mirror 19b of the prism block 19 is reflected by the total reflection mirror 1.
The light is reflected by 9a and passes through the phase spatial light modulator 17, and at that time, the phase of the light is spatially modulated according to a predetermined modulation pattern to become a recording reference light. The recording reference light passes through the convex lens 16 and is converged. Part of the light amount of the recording reference light is reflected by the half mirror 15a of the prism block 15 and passes through the two-part optical rotatory plate 14.

Here, the optical rotation plate 14L of the two-division optical rotation plate 14
The polarization direction of the laser beam that has passed through is rotated by + 45 ° to become an A-polarized laser beam, and the laser beam that has passed through the optical rotation plate 14R is rotated by -45 ° and becomes a B-polarized laser beam. The A-polarized and B-polarized recording reference lights that have passed through 14 are recorded on the optical disc recording medium 1
And is once converged by the objective lens 12 before the boundary surface between the hologram recording layer 1c and the substrate 4, and then passes through the hologram recording layer 1c while diverging.

To facilitate understanding, the polarization of light will be briefly described. A-polarized light is a straight line obtained by rotating S-polarized light by −45 ° or P-polarized light by + 45 °. The B-polarized light is a linearly polarized light obtained by rotating the S-polarized light by + 45 ° or rotating the P-polarized light by −45 °. Therefore, the polarization directions of the A-polarized light and the B-polarized light are orthogonal to each other.

FIGS. 15 and 16 are explanatory views showing the state of the laser beam during recording. In the figure, reference numeral 8
The symbol indicated by 1 indicates P polarized light, the symbol indicated by 83 indicates A polarized light, and the symbol indicated by 84 indicates B polarized light. In FIG. 15, the optical rotation plate 1 of the two-part optical rotation plate 14
The information light 71L that has passed through 4L becomes A-polarized light, is irradiated onto the optical disk recording medium 1 by the objective lens 12, passes through the hologram recording layer 1c, is converged on the reflection film 1d, and is reflected by the reflection film 1d. Then, it goes back inside the hologram recording layer 1c again.

The recording reference light 72L that has passed through the optical rotator 14L of the two-part optical rotator 14 becomes A-polarized light, which is irradiated onto the optical disc recording medium 1 by the objective lens 12 and is incident on the hologram recording layer 1c. After converging once above, it passes through the hologram recording layer 1c while diverging.
Then, in the hologram recording layer 1c, the reflection film 1d
The A-polarized information light 71L reflected by and the A-polarized recording reference light 72L traveling toward the reflection film 1d interfere with each other to form an interference pattern three-dimensionally in the hologram recording layer.
Therefore, when the output of the light emitted from the laser light source 25 becomes high, the interference pattern is stereoscopically recorded in the hologram recording layer 1c.

Further, as shown in FIG. 16, the information light 71R which has passed through the optical rotation plate 14R of the two-division optical rotation plate 14 becomes B-polarized light, which is irradiated onto the optical disk recording medium 1 by the objective lens 12 and hologram recording is performed. Passing through layer 1c,
It converges on the reflection film 1d, is reflected by the reflection film 1d, and again travels in the opposite direction in the hologram recording layer 1c.
The recording reference light 72R that has passed through the optical rotation plate 14R of the two-division optical rotation plate 14 becomes B-polarized light, and the objective lens 12
The optical disc recording medium 1 is irradiated with the light, converges once on the incident surface of the hologram recording layer 1c, and then passes through the hologram recording layer 1c while diverging. Then, in the hologram recording layer 1c, the B-polarized information light 71R reflected by the reflection film 1d and the B-polarized recording reference light 72R traveling toward the reflection film 1d interfere with each other to form a three-dimensional interference pattern. When the output of the light emitted from the laser light source 25 becomes high, the interference pattern is stereoscopically recorded in the hologram recording layer 1c.

In the hologram recording mode of the optical disk recording medium of the present invention shown in FIGS. 15 and 16, the information beam is arranged so that the optical axis of the information beam and the optical axis of the recording reference beam are arranged on the same line. And the recording reference light are applied to the hologram recording layer 1c from the same surface side. Further, by performing the recording operation a plurality of times on the hologram recording layer 1c at the same recording position in the information recording area by changing the modulation pattern of the recording reference light, it is possible to multiplex record the information by phase encoding multiplexing. Is.

Thus, in the recording apparatus for recording a hologram on the optical disk recording medium of the present invention, a reflection type (Lippmann type) hologram is formed in the hologram recording layer 1c. The A-polarized information light 71L and the B-polarized recording reference light 72R do not interfere with each other because their polarization directions are orthogonal to each other. Similarly, the B-polarized information light 71R and the A-polarized recording reference light 72L are different from each other. , The polarization directions are orthogonal, so there is no interference. That is, when recording a hologram, there is an advantage that extra interference fringes can be prevented from occurring and a reduction in the SN (signal to noise) ratio can be prevented.

Further, in the above recording apparatus, the information light is irradiated so as to converge on the boundary surface between the hologram recording layer 1c and the substrate 1e in the optical disc recording medium 1 as described above, and the reflecting film 1d of the optical disc recording medium 1 is irradiated. Is reflected by and returns to the objective lens 12 side. This return light is incident on the four-division photodetector 29 in the same manner as during servo. Therefore, it is possible to perform the focus servo in the address servo area 6 even at the time of recording, by using the information light incident on the four-division photo detector 29.

The recording reference light is converged on the incident surface of the hologram recording layer 1c of the optical disc recording medium 1 and the embossed pits in the servo area 6 are irradiated with divergent light. Even if the light is reflected by the reflection film 1d and returned to the objective lens 12 side, it does not form an image on the four-division photodetector 29, and therefore cannot be used for focus servo.

In the above recording apparatus, by moving the convex lens 16 back and forth and changing its magnification,
In the hologram recording layer 1c, the size of the area (hologram formation area) in which one interference pattern of the information light and the reference light is stereoscopically recorded can be arbitrarily selected.

Next, the operation of reproducing the recorded information will be described with reference to FIG. 14 again. During reproduction, all pixels of the spatial light modulator 18 are turned on. In addition, the controller 50
Gives the same information as the modulation pattern of the recording reference light at the time of recording the information to be reproduced to the phase spatial light modulator 17, and the phase spatial light modulator 17 gives the modulation at the time of recording the information given by the controller 50. According to the same information as the pattern, the phase of the passing laser beam is spatially modulated, the phase of the laser beam is spatially modulated, and the reproduction reference light is generated.

The output of the laser light emitted from the laser light source 25 is switched to a low output for reproduction, and the controller 50 causes the servo clock C reproduced from the reproduction signal RF.
Based on K, the timing at which the laser beam passing through the objective lens 12 passes through the hologram recording area 7 is predicted, and while the laser beam from the objective lens 12 passes through the hologram recording area 7, the above-mentioned setting during reproduction is set. To do. Therefore, while the laser beam from the objective lens 12 passes through the hologram recording area 7, focus servo control and tracking servo control are not performed, but only tracking servo control is performed.

As shown in FIG. 14, the P-polarized laser beam emitted from the laser light source 25 is converted into a parallel light beam by the collimator lens 24, passes through the beam splitter 30, and enters the beam splitter 23. A part of the light amount is reflected by the half mirror 23a and is incident on the photodetector 26 for automatic light amount adjustment. The laser beam passing through the half mirror 23a is incident on the prism block 19. Part of the light incident on the prism block 19 is reflected by the half mirror 19b, and the reflected light is reflected by the total reflection mirror 19a and passes through the phase spatial light modulator 17, at which time a predetermined modulation is performed. According to the pattern, the phase of the light is spatially modulated and becomes the reproduction reference light.

The reproduction reference light becomes light that passes through the convex lens 16 and converges. A part of the reproducing reference light is reflected by the half mirror 15a of the prism block 15,
It passes through the two-part optical rotation plate 14. Here, the two-part optical rotation plate 1
The light passing through the optical rotation plate 14L of No. 4 has its polarization direction rotated by + 45 ° to become A-polarized light, and the light passing through the optical rotation plate 14R has its polarization direction rotated by −45 °, and becomes B-polarized light. Become. The reproduction reference light that has passed through the two-part split optical rotation plate 14 is
The optical disc recording medium 1 is irradiated with the light through the objective lens 12, converges before the hologram recording layer 1c, and then passes through the hologram recording layer 1c while diverging.

In FIGS. 17 and 18, the symbol denoted by reference numeral 81 represents P-polarized light, the symbol denoted by reference numeral 82 represents S-polarized light, the symbol denoted by reference numeral 83 represents A-polarized light, and denoted by reference numeral 84. The symbol indicates B-polarized light. In FIG. 17, the reproduction reference light 73L that has passed through the optical rotation plate 14L of the two-division optical rotation plate 14 becomes A-polarized light, which is irradiated onto the optical disc recording medium 1 by the objective lens 12 and converges on the front side of the hologram recording layer 1c. , While passing through the hologram recording layer 1c. As a result, the hologram recording layer 1
From c, the reproduction light 74L corresponding to the information light 71L at the time of recording is generated. This reproduction light 74L is generated by the objective lens 1
The light travels to the second side, is converted into a parallel light beam by the objective lens 12, passes through the two-divided optical rotation plate 14 again, and becomes S-polarized light.

Further, as shown in FIG. 18, the reproduction reference light 73R that has passed through the optical rotator 14R of the two-division optical rotator 14 becomes B-polarized light, which is irradiated onto the optical disk recording medium 1 by the objective lens 12 to generate a hologram. After converging on the front side of the recording layer 1c, it passes through the hologram recording layer 1c while diverging. As a result, reproduction light 74R corresponding to the information light 71R at the time of recording is generated from the hologram recording layer 1c. The reproduction light 74R travels toward the objective lens 12, is converted into a parallel light beam by the objective lens 12, passes through the two-divided optical rotation plate 14 again, and becomes S-polarized light.

The reproduced light which has passed through the two-divided optical rotation plate 14 is incident on the prism block 15 and a part of it is transmitted through the half mirror 15a. The reproduction light transmitted through the half mirror 15a is reflected by the total reflection mirror 15b, passes through the spatial light modulator 18 in which all pixels are turned on, and a part of the light amount is reflected by the half mirror 19b of the prism block 19. , C
The light enters the CD array 20, and an on / off pattern of the spatial light modulator 18 at the time of recording is imaged on the CCD array 20. By detecting this pattern, the pattern is recorded on the optical disc recording medium 1. The information is played.

When a plurality of pieces of information are multiplex-recorded on the hologram recording layer 1c by changing the modulation pattern of the recording reference light, the same modulation as the modulation pattern of the recording reference light is included in the plurality of pieces of information. Only the information read by the reference light for reproducing the pattern is reproduced. 17 and 18
In the example, the optical axis of the reproduction reference light and the optical axis of the reproduction light are arranged on the same line, and the irradiation of the reproduction reference light and the collection of the reproduction light are performed from the same side of the hologram recording layer 1c. is there.

Further, part of the reproduction light is a four-divided photodetector 29 like the return light at the time of servo during recording.
Incident on. Therefore, this 4-division photo detector 29
It is possible to perform focus servo in the servo area 6 even at the time of reproduction by using the light incident on. It should be noted that the reproduction reference light is once converged on the front side of the hologram recording layer 1c in the optical disc recording medium 1 and becomes divergent light in the hologram recording layer 1c, so that the optical disc recording medium 1
Even if the light is reflected by the reflective film 1d and returned to the objective lens 12 side, no image is formed on the four-division photodetector 29.

In carrying out the present invention, as the laser beam for irradiating the optical disc recording medium 1 from the optical head, the laser beam of the wavelength λ ₂ for hologram formation emitted from the laser light source 25 and the moving optical disc recording medium 1 are used. The servo provided in the servo area 6 for performing the tracking servo control for the optical head so that the irradiation position of the laser beam for hologram formation may follow the information recording position of the optical head for the time required for the exposure without displacement. Clock pit SCK
1 to 3 are irradiated with the tracking laser beam to detect the positional deviation between the information recording position and the irradiation position of the laser beam for hologram formation in the moving direction of the optical disc recording medium,
The optical head 11 for the optical disc recording medium 1 of the present invention is, for example, coherent with a plurality of wavelengths λ ₁ and λ ₂ because it requires a tracking laser beam having a wavelength λ ₁ emitted from the laser light source 33. It is configured to emit a laser beam.

The combinations of a plurality of wavelengths λ ₁ and λ ₂ are as follows: λ ₁ = 780 nm, λ ₂ = 532 nm, λ ₁ = 780 nm, λ ₂ = 650 nm, λ ₁
= 650 nm, λ ₂ = 525 nm combination, λ ₁ = 650
nm, λ ₂ = 405 nm combination, λ ₁ = 780 nm, λ ₂
= 390 nm combination and the like. In the device of FIG. 14,
An apparatus provided with two laser light sources 25 and 33 having different wavelengths has been exemplified, but a plurality of wavelengths including a combination of a single laser light source and a wavelength selection element such as a prism or a diffraction grating instead of the two types of laser light sources. A tunable laser light source device capable of emitting a laser beam, or a tunable laser light source device using a laser beam source and a nonlinear optical system for exchanging the wavelength of light emitted from the laser beam source can also be used. .

In sequentially recording holograms at information recording positions in the hologram recording area 7 of the optical disc recording medium 1, a positional deviation occurs while the optical disc recording medium 1 is moved by a distance of at least 200 μm by the laser beam for hologram formation. It is necessary to fix the hologram on the hologram recording layer by following the information recording position and continuing irradiation.

Then, the optical disk recording medium 1 is 200 μ
When the hologram recording is completed by moving m, the optical head suddenly returns in a direction opposite to the moving direction of the optical disc recording medium 1 by 200 μm-α (where α is the distance between adjacent information recording positions). In order to record a new hologram at the next information recording position of the optical recording medium in the same recording manner,
Irradiation to the next information recording position is started by the hologram forming laser beam, and while the optical disc recording medium 1 is moved by 200 μm, the information recording position is accurately tracked to the information recording position while being followed by the hologram forming laser beam. Perform hologram recording.

Such a hologram recording operation is sequentially repeated until the next servo area is reached. While the optical head passes through the servo area 6, the focus servo control and the tracking servo control are performed as described above, and when moving to the information recording area of the next sector, the hologram recording operation similar to the above is performed while performing the tracking servo control. Repeatedly, holograms are sequentially recorded at the information recording position of the information recording area of the next sector.

[0078]

As described above, according to the present invention,
When recording a hologram in the hologram recording area,
Since the hologram recording spot recorded on one track of the hologram recording area and the hologram recording spot recorded on the track adjacent thereto are recorded at different positions in the circumferential direction, at least 1 is recorded on each track.
Two hologram recording spots will be formed,
The hologram recording operation and the hologram reproducing operation are not burst-like and are continuous processing. Moreover, according to the recording method of the present invention, when the diameter of the hologram recording spots is D and the number of multiplexed hologram recording spots is m, the pitch P between adjacent hologram recording spots is P = D / m. To record. Therefore, it is possible to efficiently record the hologram in the hologram recording area of the optical disc recording medium with high density, and it is possible to increase the density of the hologram recording capacity.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an optical disc recording medium used in an optical disc recording device according to an embodiment of the present invention.

FIG. 2A is a partially enlarged view of FIG. 1.

FIG. 2B is a partially enlarged view of FIG. 1.

FIG. 3 is an enlarged partial sectional view of the optical disc recording medium.

FIG. 4 is a graph showing the relationship between the spatial frequency of pits and the transfer function (MTF).

FIG. 5 is a diagram for explaining a conventional servo pit.

FIG. 6 is a diagram for explaining servo pits formed on the optical disc recording medium.

FIG. 7 is a diagram showing an arrangement relationship between each track and each frame of the optical disc recording medium and address information.

FIG. 8 is a diagram for explaining a hologram recording format.

FIG. 9 is a timing chart showing a recording pulse that gives timing at the time of recording.

FIG. 10 is a diagram for explaining another embodiment of the hologram recording format.

FIG. 11 is a diagram showing zones formed on the optical disc recording medium.

FIG. 12 is a block diagram schematically showing a configuration of an optical disc recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of a portion related to a tracking error detection circuit in the signal processing circuit of the device.

FIG. 14 is a schematic diagram showing an example of an optical system of an optical head of the same apparatus and showing a principle of an optical portion of an optical head used for the apparatus.

FIG. 15 is an explanatory diagram showing a state of a laser beam during recording.

FIG. 16 is an explanatory diagram showing a state of a laser beam during recording.

FIG. 17 is an explanatory diagram showing a state of a laser beam during reproduction.

FIG. 18 is an explanatory diagram showing a state of a laser beam during reproduction.

FIG. 19 is an enlarged partial sectional view of a part of a conventional optical disc recording medium using volume holography.

[Explanation of symbols]

1 ... Optical disc recording medium, 1a, 1b ... Transparent substrate, 1c
... recording layer, 1d ... reflective film, 1e ... substrate, 2 ... frame,
3 ... Segment, 4 ..., 5 ..., 6 ... Servo area, 7 ... Hologram recording area, 8 ... Address area, 8a ... Preamble, 8b ... Sync mark, 8c ... Address part, 8
d ... end address mark, 8e ... post synchronization mark,
8f ... Postamble, 10 ... Optical disk recording / reproducing apparatus, 11 ... Optical head, 12 ... Objective lens, 13 ... Actuator, 14 ... Two-division optical rotation plate, 15, 19, 23,
30 ... Prism block, 15a, 19b, 23a, 3
0a ... half mirror, 15b, 19a ... total reflection mirror,
16, 27 ... Convex lens, 17 ... Phase spatial light modulator, 18
... Spatial light modulator, 24, 32 ... Collimator lens, 2
5, 33 ... Laser light source, 26, 31 ... Photodetector, 28 ... Cylindrical lens, 29 ... 4-division photodetector, 30a ... Half mirror, 40 ... Optical head,
41 ... Spindle, 42 ... Spindle motor, 43 ... Spindle servo circuit, 44 ... Drive device, 45 ... Detection circuit, 46 ... Focus servo circuit, 47 ... Tracking servo circuit, 48 ... Slide servo circuit, 49 ... Signal processing circuit, 50 ... controller, 51 ... operation unit, 52 ... tilt detection circuit, 53 ... tilt correction circuit, 54 ... tracking control circuit, 55 ... tracking servo circuit, 61 ... differential amplifier, 62 ...
Multiplexer, 63 ... Comparator, 64 ... Logical operation circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaharu Kinoshita             2-5-1 Shin-Yokohama, Kohoku Ward, Yokohama City, Kanagawa Prefecture             Nissou 13th Building 7th floor Optware Co., Ltd.             Within (72) Inventor Hozumi Tanaka             2-5-1 Shin-Yokohama, Kohoku Ward, Yokohama City, Kanagawa Prefecture             Nissou 13th Building 7th floor Optware Co., Ltd.             Within (72) Inventor Takao Yamamoto             2-5-1 Shin-Yokohama, Kohoku Ward, Yokohama City, Kanagawa Prefecture             Nissou 13th Building 7th floor Optware Co., Ltd.             Within F term (reference) 2K008 AA00 AA04 BB04 BB05 BB06                       CC01 CC03 DD13 FF07 HH06                       HH18 HH26                 5D090 AA01 BB20 CC01 CC04 DD03                       FF11 FF50 KK12 KK14

Claims (7)

[Claims] 1. A servo area for tracking servo, focus servo and clock generation of an optical head is discretely formed at predetermined intervals in the circumferential direction, and a servo area is formed between each servo area when no recording is performed. In the recording method of the optical disc recording medium, a hologram recording area is formed, and an interference pattern due to interference between the information light emitted from the optical head and the recording reference light is recorded as a hologram in the hologram recording area. A hologram recording spot recorded on one track of a recording area and a hologram recording spot recorded on a track adjacent thereto are recorded at different positions in the circumferential direction, and a pitch between adjacent hologram recording spots. P is the diameter of the hologram recording spot, D is the preset hologram recording When the multiplexing number of spots is m, the recording method of an optical disc recording medium characterized by recording the hologram recording spot on the hologram recording area such that P = D / m. 2. An interval between a hologram recording spot recorded on one track of the hologram recording area and a hologram recording spot recorded on a track adjacent thereto is substantially P, and on the one track. 7. A hologram is recorded in the hologram recording area so that the hologram recording spot recorded on the track and the hologram recording spot recorded on a track m tracks away from the hologram recording spot are equal in circumferential direction. 1. A recording method for an optical disk recording medium according to 1. 3. An interval between a hologram recording spot recorded on one track of the hologram recording area and a hologram recording spot recorded on a track adjacent to the hologram recording spot is substantially P, and the hologram recording spot is recorded on the one track. A hologram is recorded in the hologram recording area such that the position in the circumferential direction of the hologram recording spot recorded on the track and the position of the hologram recording spot recorded on the track separated by m tracks are displaced from each other by P / 2. Item 2. A recording method for an optical disk recording medium according to item 1. 4. The optical disk recording medium is divided into a plurality of zones in the radial direction, and the number of hologram recording spots recorded in the circumferential direction of one of the hologram recording areas in the outer peripheral side is equal to that of the inner peripheral side. 4. A hologram is recorded in the hologram recording area so as to be larger than the number of hologram recording spots recorded in the circumferential direction of the hologram recording area in one of the zones.
A recording method for an optical disk recording medium according to any one of 1. 5. A pit for clock generation is formed in the servo area, and a signal for determining a recording timing for each track is generated with the pit for clock generation as a reference. 5. A recording method for an optical disk recording medium according to any one of items 4 to 4. 6. Servo areas for tracking servo, focus servo and clock generation of the optical head are discretely formed at predetermined intervals in the circumferential direction, and between the servo areas are mirror areas when not recorded. A hologram recording area is formed, and the hologram recording area is recorded with the hologram on an optical disc recording medium in which an interference pattern due to interference between the information light emitted from the optical head and the recording reference light is recorded as a hologram. In the optical disc recording apparatus, a clock generation unit that reads information in the servo area of the optical disc recording medium by the optical head to generate a clock, and a recording timing for each track based on the clock generated by the clock generation unit Recording timing generating means for generating a recording timing signal to be determined, and The recording timing generation means records a hologram recording spot recorded on one track of the hologram recording area and a hologram recording spot recorded on a track adjacent thereto at different positions in the circumferential direction. And the pitch P between adjacent hologram recording spots
However, if the diameter of the hologram recording spot is D and the preset multiple number of hologram recording spots is m,
An optical disk recording apparatus, wherein the recording timing of the hologram in the hologram recording area is determined so that P = D / m. 7. A servo area for tracking servo, focus servo, and clock generation of the optical head is discretely formed at predetermined intervals in the circumferential direction, and the optical head emits light between the servo areas. In an optical disc reproducing device for reproducing an optical disc recording medium in which a hologram recording region in which an interference pattern due to interference between information light and recording reference light is recorded as a hologram is formed, information in a servo region of the optical disc recording medium is recorded in the optical head. And a reproduction timing generation unit for generating a reproduction timing signal for determining a reproduction timing for each track with reference to the clock generated by the clock generation unit. The generating means is on one track of the hologram recording area. And a hologram recording spot recorded on a track adjacent thereto are recorded at different positions in the circumferential direction, and a pitch P between adjacent hologram recording spots is recorded.
However, when the diameter of the hologram is D and the preset number of multiplexed holograms is m, the reproduction timing of the hologram from the hologram recording area is determined so that P = D / m. A characteristic optical disk reproducing apparatus.